A. Technical Field
The present invention pertains generally to digital image processing, and relates more particularly to image processing that enables fast segmentation of an image.
B. Background of the Invention
A digital image typically comprises an array of picture elements. Each picture element, also known as a “pixel,” has a value and a location within the array. The value represents either the intensity of the pixel (if in grayscale) or the color of the pixel. At a higher level, pixels may be segmented into two or more groups. For example, pixels of an image may be classified into foreground and background layers or segments.
When processing a digital image, it can be beneficial to differentiate the pixels into different segments. Certain segments of the image may be of more interest than other segments, may be beneficially affected by image processing procedures, or may be adversely affected by image processing procedures. By dividing an image into different segments, one segment may be processed differently than another segment. Different methods for segmenting an image exist. Depending upon the application, it is generally preferred to have a good segmentation process that is efficient and not computationally expensive. The output of post-processing may also be affected by the method of segmentation that is used.
For example, one application of segmentation is document compression. Although compression methods help reduce file sizes, the compressed files are typically not without problems. Conventional image compression approaches that compress an entire image generally lead to unsatisfactory results in reconstructed image quality and compressed file size. When a high compression ratio is used, the compressed images may show disturbing artifacts, such as blurred text and blurred color boundaries. To obtain a high-quality compressed image, the compression ratio may need to be set very low, but the resulting file size will therefore not be substantially reduced. Thus, neither approach is particularly satisfactory. By segmenting an image into foreground and background regions, the foreground may be compressed at a different level than the background.